Northern Ireland police are assessing the impact on a murder inquiry of the IRA's announcement that it has expelled three of its members.

The family of Robert McCartney accused IRA members of responsibility for his murder and of intimidating witnesses.

The IRA said one of those expelled made a statement to a solicitor and called on the others to take responsibility.

Two of the men dismissed were described by the IRA as "high ranking volunteers".

The McCartney family has said it will consider the IRA statement and may comment on Saturday.

Sinn Fein's Gerry Adams has said that people have a patriotic duty to support the family of the dead man, who died after being stabbed outside a bar near Belfast city centre four weeks ago.

'Huge pressure'

The expulsions came after what the IRA called "an investigation" into last month's killing.

BBC Northern Ireland security editor Brian Rowan said: "Given the events of recent days there was an inevitability about this latest statement from the IRA.

"Republicans had been under huge pressure to do something, and in its statement tonight, the IRA said any intimidation or threats made in its name would not be tolerated."

There were 12 Provos involved and some of the culprits are being protected by sacrificing these three

Alasdair McDonnellSDLP

DUP assembly member Ian Paisley Jnr said: "No one should be fooled by this diversionary tactic of a pretend purge of the IRA ranks.

"The statement only highlights the confusion that exists within the IRA who last week told us they were not involved in criminality and tonight pretend they have purged those who are criminals."

SDLP deputy leader Alasdair McDonnell said: "They offered three out of a gang of 12 who not only murdered Robert McCartney but concealed evidence and obstructed the investigation.

"There were 12 Provos involved and some of the culprits are being protected by sacrificing these three."

Mr Ahern said Sinn Fein should turn killers in

Ulster Unionist Sir Reg Empey said unless the expulsions were accompanied "by the names of the individuals involved in a way that will lead to police prosecution", the statement would be viewed as little other than "a cynical face-saving exercise".

The IRA statement came 24 hours after Sinn Fein President Gerry Adams met the McCartney family.

The family had accused republicans of pressuring witnesses not to talk, although they welcomed an earlier IRA statement urging his killers to come forward.

'Support for campaign'

Mr Adams described the meeting as "constructive". "There is an onus on us to do everything we can to bring closure to this family," he said.

He said that he was told up to 70 people, and up to 21 this week, had already come forward with information about his death.

Taoiseach Bertie Ahern has said that a test of Sinn Fein's stated opposition to criminality would be to turn in the killers.